A Wii U remote is just a -TR Wii Remote Plus, and they work fine with Dolphin. However, the MS Bluetooth Stack, the default windows bluetooth stack, does not work with -TR wiimotes. You'd need either the Toshiba Stack (lots of setup) or the DolphinBar (easy) to get a -TR wiimote to work on windows. Both of those solutions require unique hardware, but we have hardware that works with them on our Recommended Accessories page.

Alternatively, you can just get a standard wiimote (not plus) and you can use it on any bluetooth stack if you wish. Of course you'd still need a bluetooth adapter, so you might as well just get a dolphinbar if you don't have bluetooth already.

Just don't get 3rd party wiimotes or shady super cheap ones from the internet.